The detection of minute quantities of biochemical substances in a specimen of animal body fluid is important, for example, in the early detection of disease. Conventional methods of specimen analysis that are feasible in a commercial setting include Enzyme Linked Immunosolvent Assay (ELISA), Western blot, Immunofluorescent, and Heme Agglutination (HA). These methods may be performed automatically by equipment including the “System 36 AutoBlot” marketed by Genelabs Diagnostics (Singapore) a subsidiary of Genelabs Technologies, Inc.; or the “Automated RIBA Processor” marketed by Chiron Corp. Other laboratory instrumentation may be used manually, including an ELISA plate reader, a fluorometer, and/or a luminometer. Conventional automatic equipment is bulky and expensive to acquire and maintain. And, manual equipment is labor intensive to use. Consequently, specimen analysis is costly. In some communities, a lack of specimen analysis has led to lengthy turn around delays. Such costs and delays interfere with the wide application of specimen analysis as a diagnostic practice. As a result, disease in animals including humans continues unchecked in its early stages.
A conventional biochemical assay performed in a laboratory may include the detection of microscopic paramagnetic particles (PMPs) bound to a giant magnetoresistive (GMR) sensor by specific intermolecular recognition bonds. PMPs are detected as a difference in the resistance of a GMR sensor having a bound PMP compared to a reference GMR sensor having no bound PMP. The difference may be detected using sinusoidal magnetic bias for the GMR sensors and a conventional lock-in amplifier technique. Accuracy of the assay depends in part on the removal of PMPs not bound according to the specific intermolecular recognition bond of interest.
The biochemical assay described above is prohibitively expensive for commercial application outside a laboratory setting. Part of this cost is in labor intensive steps including manual preparation of the specimen in combination with PMPs and manual removal of PMPs to improve assay accuracy. Another part of the cost becomes prohibitive as the number specimens to be tested in a given period of time is increased to a commercially practical level. Without method steps that prevent exposure of common surfaces to more than one specimen, an unsatisfactory risk of false positive assays may result.
In light of the demand for high volume biochemical assay services in combination with the lack of satisfactory techniques for maintaining low cost per specimen and low probability of false positive results, the need remains for improved systems and methods for biochemical assay.